Instrument for interrupting conduction paths within the heart

ABSTRACT

A probe for making transmural lesions in one or more walls of the atria of the heart in open-heart surgery. The lesion blocks electrical impulses in a direction crosswise to the lesion. The probe has a handle ( 1 ), a closed electrode ( 2 ) at an end of the probe, a relatively rigid member ( 5 ) of physiologically acceptable plastic connecting the probe and the electrode, and means ( 6, 7 ) for coupling the probe to an RF power source.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation of application Ser. No. 09/583,303, filedMay 30, 2000, which is a divisional of application Ser. No. 09/180,124filed Nov. 2, 1998, which is the U.S. national phase of PCT applicationNo. PCT/NL97/00223 filed Apr. 25, 1997, which claims priority fromNetherlands application No. 1003021, filed May 3, 1996.

FIELD OF THE INVENTION

[0002] The invention relates to an instrument for making at least onetransmural lesion in one or more walls of the atria of the heart, whichlesion essentially blocks the electrical impulse conduction in adirection crosswise to the transmural lesion.

BACKGROUND OF THE INVENTION

[0003] All kinds of heart arrhythmias, and in particular chronic andparoxysmal atrial fibrillation, can currently be treated by surgery.

[0004] A known surgical procedure (MAZE) was designed to eliminateatrial fibrillation permanently. In this procedure incisions are madewith a scalpel in the walls of the atria, in order to block electricalimpulse conduction in a direction crosswise to the incisions, by theinterruption of the tissue continuity. As a result of the subsequentscarring, these electrical blocks acquire a permanent character.

[0005] This known technique is as yet performed only to a limited extentworldwide, owing to the complexity of the operation. The increased riskis particularly associated with the duration of the operation and theway in which the operation has to be carried out.

[0006] The duration of the operation, and in particular the cross-clamptime (x-clamp) is so long that there is a great risk of damage to theheart muscle.

[0007] The cross-clamp time required for the MAZE procedure alone iscurrently still an average of 68 min. (range 50-102 min.), and thenecessary time on the heart-lung machine is on average 182 min. (range130-256 min.). For further data you are referred to AtrialFibrillations: Mechanisms and Therapeutic Strategies, Futura PublishingCo. Inc. Armonk, N.Y. 1994. J. L. Cox: Surgical Interruption of AtrialReentry as a Cure for Atrial Fibrillation. The way in which theoperation is performed with the scalpel produces an increased risk ofvascular suture leaks and subsequent bleeding, due to the large numberand location of the vascular sutures involved.

SUMMARY OF THE INVENTION

[0008] The object of the present invention is to provide an instrumentof the above-mentioned type which eliminates the abovementioneddisadvantages, and which in particular shortens the time required forthe operation and reduces the risk of bleeding and damage, thereforereducing the risk for the patient in open-heart surgery.

[0009] According to the invention, the instrument indicated ischaracterized in that the instrument is a probe in which the end whichduring the operation comes into contact with the wall to be treated is aclosed electrode which can interact with an RF power source, while theprobe is of a relatively rigid type.

[0010] The instrument according to the invention is a probe by means ofwhich in open-heart surgery it is possible to make a permanent change inan atrial wall which is transmural, i.e. it extends over the entirethickness of the wall.

[0011] As will be discussed at a later stage, during the performance ofthe operation the electrode at the end of the probe is brought intocontact with the atrial wall to be treated and is moved along it in alinear pattern. On excitation of the electrode with RF power, dielectric(RF) heating of the wall tissue occurs. The RF treatment produces achange in the cell structure of the atrial wall, with the result thatelectrical impulse conduction in a direction crosswise to the transmurallesion is blocked.

[0012] In order to be able to work well with it, the probe must be of arelatively rigid type, so that the electrode can be accuratelypositioned on and moved along the atrial wall. In the operation nodisintegration of the tissue of the atrial wall occurs, and there is norisk of subsequent bleeding. The operation can be carried out on theoutside or the inside of the atrium as desired.

[0013] Methods of RF heating or dielectric heating are based on the useof heat generated in materials which are relatively poor electricalconductors when they are placed in high-frequency electromagneticfields. The heat is generated as a result of dielectric losses occurringin a material situated between metal electrodes which form a capacitorwhich is connected to a high-frequency (RF) generator. Such heating ishighly uniform and therefore extremely suitable for use of theinstrument, the probe, according to the invention. During use of theprobe, one of the capacitor “plates” is formed by the electrode at theend of the probe, while the other “plate” is a counter-electrode whichis stuck on, for example, the patient's back; when the latter electrodeis being placed, it is preferable to use a contact gel which haselectrical conductance. Of course, the counter-electrode can also beplaced on the outside of the atrial wall of the heart, for example ifthe electrode of the probe is being brought into contact with the insideof said wall.

[0014] In connection with the invention, reference is made to WO95/03742, which discloses a catheter comprising at the distal a metalelectrode by means of which tissue erosion, also known as ablation, canbe carried out.

[0015] Such a catheter typically has a length of approximately 1 meter,a diameter of approximately 2 mm, and has an electrode of approximately2 mm diameter, and its low thickness makes it very flexible, so that itcan follow a blood vessel without any problems. This catheter issuitable for local punctate ablation. Such a catheter is not suitablefor use as a probe for making stripe-shaped transmural lesions in anatrial wall.

[0016] In particular, the probe according to the invention has at leasta handle; an end; a relatively rigid member, such as a shaft, betweenthe handle and the end, and connecting and conduction means forconnecting the end of the probe to an RF power source.

[0017] In the instrument according to the invention a temperaturerecorder is advantageously present near the end of the probe, whichtemperature recorder, operating in a feedback system with the RF powersource, can regulate the temperature of the end of the probe to a presetvalue. Through input of the RF power, the temperature of the end of theprobe will generally rise; feedback with the RF power source makes itpossible to ensure that the temperature of the end does not exceed apredetermined value.

[0018] With use of RF power it is extremely important that the fewestpossible electrical blockages should be present in the body sectionbetween the end of the probe and the counter-electrode on the outside ofthe body. On account of this, it is preferable to ensure that the probecan interact with means for supplying a physiologically acceptableliquid to the end thereof. In its simplest form, such a liquid issupplied near the electrode of the probe by way of a line which does notform part of the probe. The function of the liquid is, on the one hand,to cool the electrode and, on the other, to prevent the occurrence ofelectrically insulating air gaps which adversely affect the efficiencyof the RF action.

[0019] It is very advantageous for the probe according to the inventionitself to have means for discharging a physiologically acceptable liquidnear the end of the probe. Said liquid will generally preferably have acertain degree of electrical conduction, and is expediently aphysiological salt solution.

[0020] In a very attractive embodiment, the instrument has between thehandle of the probe and the shaft inlet means for introducing thephysiologically acceptable liquid, which inside the shaft remainselectrically insulated from the connecting and conduction means presentin the shaft, while near the end it has outflow means for thephysiologically acceptable liquid. With this embodiment, the functioningof the probe can be improved yet further, and it can be ensured that thegreatest RF energy effect is concentrated in the wall of the atrium tobe treated, forming the desired transmural lesion.

[0021] At the side of the handle facing away from the end of the probe,the conduction and connecting means of the probe according to theinvention comprise a connector connected thereto, with contact means forconnection of the electrode to the end of the probe and the temperaturerecorder present therein to the RF power source.

[0022] The connector is preferably of the rapid coupling type, so thateasy coupling to the RF power source is permitted.

[0023] In order to make handling of the instrument according to theinvention, in the form of a probe, as easy as possible for the operatingsurgeon during an open-heart operation, the shaft of the probepreferably has an intrinsic curvature, which is expedientlyapproximately 140 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will now be explained with reference to thedrawing, in which:

[0025]FIG. 1 shows a schematic picture of the transmural lesions whichcan be made with the instrument according to the invention, and whichcan block electrical impulses in directions crosswise to said lesions;

[0026]FIG. 2 shows an instrument according to the invention in a firstembodiment;

[0027]FIG. 3 shows an instrument according to the invention in a secondembodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 shows diagrammatically in a two-dimensional view the twoatria of a human heart, in which the transmural lesions are indicated byreference letter C, the undisturbed electrical impulses by A, and theblocked electrical impulses by B. The lesions C are in the nature ofscar tissue which is formed after treatment using the probe according tothe invention. The atria, as viewed epicardially, include the leftatrium 100 and the right atrium 101. Structural features of the atriainclude the pulmonary veins 110, the inferior vena cava 120, thesuperior vena cava 130, the left atrial appendage 140 and the rightatrial appendage 150. A first lesion 160 is a curved lesion that isjoined end-to-end such that it encircles the pulmonary veins 110, and isbetween the pulmonary veins 110 and conductive pathways in the leftatrium 100 and between the pulmonary veins 110 and conductive pathwaysin the right atrium 101. A second lesion 165 extends between thesuperior vena cava 130 and the inferior vena cava 120 and blocks a firstconductive pathway 167. A third lesion 170 extends across the leftatrium 100 from an intersection 171 with a portion of the first lesion160 toward the left atrial appendage 140 and blocks a second conductivepathway 172. A fourth lesion 175 extends along the right atrium 101laterally from an intersection 176 with a portion of the second lesion165. A fifth lesion 180 extends from a portion of the first lesion 160along the left atrium 100 and blocks a third conductive pathway 182. Asixth lesion 185 extends along the right atrium 101 toward the rightatrial appendage 150.

[0029]FIG. 2 shows a probe according to the invention in a firstembodiment, and shows a handle 1, an active metal end 2 as a closedelectrode with indication of the position of a temperature sensor 3. Theshaft of the probe 5 has a curvature 4 of approximately 140 degrees, andinside the shaft run the electrical wires 6 for exciting the closedelectrode-type end 2 and wire 7 for connecting the temperature sensorwhich is fitted at the position of reference number 3.

[0030] Inside the handle 1 are electrical switch means 10 (not shown inany further detail) for permitting connection of the probe to the RFgenerator (not shown). Reference numbers 8 and 9 also indicate aconnector making it possible to couple the probe to the RF generator.

[0031]FIG. 3 shows a particularly advantageous embodiment of the probeaccording to the invention, which is identical to the probe of FIG. 2,but in which reference number 11 indicates a Y-connector which makes itpossible to supply a physiologically acceptable liquid by way of a port12 into the shaft 5, said physiologically acceptable liquid being guidedthrough the shaft 5 without contact with the conduction means 6 and 7.The physiologically acceptable solution flows by way of the port 12 toan inner shaft 13, and from there by way of the shaft 5 to the outflowports 14 which are disposed in the vicinity of the metal end 2. Thephysiologically acceptable liquid is expediently a physiological saltsolution which is readily tolerated by the body.

[0032] The physiological salt solution, on the one hand, achievescooling of the closed electrode 2 and, on the other hand, lowers theelectrical resistance between the closed electrode of the end 2 and theatrial wall. Extremely good and reproducible results are obtained withthe probe shown in the figure. The source of RF power is typically agenerator which can deliver a power of, for example, maximum 50 watt ata frequency of 500 kHz. The power supplied is a function of thetemperature set and the tissue contact of the electrode forming the endof the probe. The desired temperature can be set at the generator, andin general lies in the range 50 to 70 degrees C. If temperatures higherthan the given range are permitted, burning of the tissue (coagulation)will occur, with the result that an insulating layer is formed; saidlayer will make further action of the RF energy difficult, with theresult that underlying tissue is not treated fully, if at all.

[0033] The end 2 of the probe expediently comprises platinum and istypically a cylindrical shape with a diameter of 4 mm. The diameter cangenerally lie between 3 and 6 mm.

[0034] The total length of the probe without connection means istypically approximately 35 cm, the handle being approximately 20 cmlong, the shaft approximately 10 cm, and the end approximately 2 cm. Ingeneral, the length of the shaft 5 lies between 8 and 15 cm, and theshaft has a diameter between 3 and 6 mm and is made of a physiologicallyacceptable plastic. Suitable plastics are nylon 66, polypropylene andhigh-density polyethylene.

1. An instrument for supplying RF energy to body tissue, the instrumentcomprising a probe having: a handle; a closed electrode at one end ofsaid probe, the instrument being adapted to allow said electrode to beaccurately positioned on and moved along an atrium wall during openheart surgery and to make at least one transmural conduction blockinglesion in the atrium wall; a connection and conduction meanselectrically communicating with said electrode and adapted forconnecting said electrode to an RF power source; a substantially rigidmember connecting said handle and said electrode, said member formed ofa physiologically acceptable plastic; and means for supplying aphysiologically acceptable liquid to said electrode, wherein said meansfor supplying the liquid is connected to said member, wherein said probeis sufficiently rigid such that an operator grasping said handle of theinstrument can accurately position and move said electrode along anatrium wall to be treated, whereby the instrument can be used in anopen-heart operation to make at least one transmural conduction blockinglesion in the atrium wall.
 2. The instrument of claim 1, wherein saidmember has an intrinsic curvature.
 3. The instrument of claim 2, whereinsaid curvature of said member is approximately 140 degrees.
 4. Theinstrument of claim 1, wherein said member has a length betweenapproximately 8 and 15 cm.
 5. The instrument of claim 1, wherein saidphysiologically acceptable liquid is a salt solution.
 6. The instrumentof claim 1, wherein said member is a shaft.
 7. The instrument of claim6, wherein said shaft has a diameter between approximately 3 and 6 mm.8. The instrument of claim 6, wherein said means for supplying thephysiologically acceptable liquid comprises an inner shaft locatedwithin said shaft connecting said handle and said electrode.
 9. Theinstrument of claim 8, wherein said shaft connecting said handle andsaid electrode further comprises an inlet port for introducing thephysiologically acceptable liquid into said inner shaft.
 10. Theinstrument of claim 8, wherein said inner shaft comprises at least oneoutflow port disposed in the vicinity of said electrode.
 11. Theinstrument of claim 1, wherein said electrode comprises platinum. 12.The instrument of claim 1, wherein said electrode is generallycylindrical.
 13. The instrument of claim 12, wherein said electrode hasa diameter between approximately 3 mm and 6 mm.
 14. The instrument ofclaim 12, wherein said electrode has a length of approximately 2 cm.